This. When I (as an ISP) was looking into the consumer router situation 10 years ago, the protocols required to handle dynamic IPv6 assignment to end users in conjunction with PPPoE simply didn't exist. Specifically, without NAT, the ISP has to somehow delegate an IPv6 subnet to the customer for their local network. The mix of IPV6CP and DHCPv6 simply weren't able to do that, and if you've ever had to deal with this for more than a handful of customers, you know that getting $joerandomenduser to manually configure an IPv6 subnet just isn't going to work. Sure, if you can control what router every customer uses you can come up with a procedure for that, but going through the wholesale network of an incumbent means you don't have that luxury.